Refining light hydrocarbon distillates



Patented Feb. 13, 1940 umr REFINING LIGHT HYDROOARBON DISTILLATES HowardB. Batchelder and Bernard H.Shoemaker, Hammond, Ind., assignors toStandard Oil Company, Chicago, 111., a corporation of Indiana N Drawing.Application Septemberl, 1937,

Serial No. 161,962 g 10 Claims. (Cl. 196-33) This invention relates to aprocess of refining hydrocarbons and particularly refining motor fuelssuch as gasoline and motor benzol. Other hydrocarbon fuels such as thepetroleum naphthas and kerosene may also be refined by our process.

The principal object of our invention is, to remove corrosive sulfurfrom motor fuels. Another object of our invention is to refine corrosivemotor fuels and render them satisfactory when subjected to the mostrigorous corrosion tests. Still another object of our invention is toimprove the prior process of treating corrosive gasoline and naphtha sothat a more complete removalof corresive constituents is obtained in ashorter time. It is well known that gasoline and petroleum naphthasfrequently are contaminated with corrosive sulfur and sulfur compoundswhich are not removed by the ordinary refining processes 20 such astreatment with sulfuric acid, doctor, etc. In order to remove corrosivesulfur it has been previously proposed in U. S. Patent 1,668,225, May 1,1928, to add to the gasoline a small amount of mercaptan and then treatthe gasoline with 25 sodium plumbite in the presence of which themercaptan reacts with the sulfur and plumbite to form insolublelead'sulfide. Mercaptans employed were the lower mercaptans of ten car-40 to treat the oil with this reagent. We have also found that the useof the heavier mercaptans, for example butyl, amyl, hexyl and octylmercaptans, requires great care in avoiding an excess which will renderthe stock sour. At the same time, 45 if insufficient mercaptan isemployed the oil will remain corrosive and fail to pass the morestringent corrosion specifications, particularly the specification foraviation gasoline wherein a sample of the gasoline is evaporated on thesteam 50 bath in a polished copper dish and any corrosive constituentswhich it may contain are concentrated during the evaporation, producinga discoloration of the copper. In order to satisfactorily pass this testa gasoline must produce sub- 55 stantially no discoloration of thecopper.

According to our process wehave provided a method of overcoming thesedifiiculties in the'following manner. The corrosive naphtha or gasolineis first treated by dissolving therein an amount of a heaviermercaptan'insuificient to 5" effect complete refining to acorrosion-free stock. For this purpose we prefer to employ butylmercaptan, either normal, tertiary or isobutyl mercaptan. However, wemay employ any of the still heavier'mercapta'ns, such as amyl, hexyl or10 rapidly and after a few minutes of agitation'the oil is substantiallyfree of corrosive agents. In order to complete the reaction, however, wenext add a small amount of alighter mercaptan, for example ethylmercaptan, and agitate further. Although theamount of ethyl mercaptanfound necessary for this method is very small, we prefer to add anexcess rather than attempt to determine the exact quantity required forcomplete refining.

After agitating the stock with the ethyl mercaptan in the presence of aplumbite solution air is introduced into the mixture to remove excessmercaptan which occurs principallyby oxidation, although some of the lowboiling mercaptan may be directly evaporated. We have discovered thatthe lighter mercaptans, such as methyl and ethyl mercaptansparticularly, are readily oxidized by atmospheric oxygen to produceunobjectionable compounds in the presence of sodium plumbite solution.Furthermore, any minute traces of the light mercaptan which may be leftin the stock disappear on standing, apparently due to oxidationreactions occurring in the presence of air or dissolved oxygen.

We have discovered that although we employ heavy mercaptans for removingthe major portion of the corrosive materials in gasoline and naphthas,the amount of these mercaptans is less than would be required werelighter mercaptans used. The reason for this improved efficiency of theheavier mercaptans is quite obscure inasmuch as itwould be expectedthat, because of their greater molecular weight, a larger amount wouldbe required. Perhaps the heavy mercaptans form complex polysulfides onreaction with elemental sulfur and thus remove a larger amount of sulfurthan can be accounted for by the commonly accepted reaction, accordingto which the mercaptan is converted to a disulfide only. This phenomenonis well illustrated by the following example: a naphtha solutioncontaining 10 mg. of sulfur per 100 cc. was treated in one case withbutyl mercaptan and in the other case with ethyl mercaptan and thenagitated with doctor solution. Varying amounts of the mercaptans wereemployed and after the treatment the samples were tested for corrosionwith the following results:

Mercaptan used Mg./l cc. Corrosion test Ethyl mercaptan Positive.Slight. Negative. Positive. Negative.

It will be observed from these results that the heavier mercaptan ismore than twice as effective as the lighter mercaptan.

In this specification we employ the term higher molecular weightmercaptan to mean butyl mercaptan and mercaptans with hydrocarbonradicals having more than four carbon atoms and by the term lowermolecular weight mercaptans 2. The presence of claim 1 wherein thehigher molecular weight mercaptan is butyl mercaptan.

3. The process of claim 1 wherein the lower molecular weight mercaptanis ethyl mercaptan.

4. The process of claim 1 wherein the higher molecular weight mercaptanis tertiary butyl mercaptan.

5. The process of claim 1 wherein the higher molecular weight mercaptanis isobutyl mercaptan.

6. The process of completely eliminating corrosive sulfur from gasolineand light hydrocarbon distillates which comprises subjecting saiddistillates to the action of a sodium plumbite solution in the presenceof added higher molecular weight mercaptan, the amount of which has beendetermined to be insufficient for complete removal of sulfur effecting achemical reaction between the said mercaptan and the sulfur in saidgasoline whereby said added mercaptan is consumed adding a lowermolecular weight mercaptan in an amount in excess of that required forcompletely removing the sulfur, agitating with sodium plumbite solutionand finally removing excess lower molecular weight mercaptan byoxidation with gaseous oxygen and separating said hydrocarbon distillatefrom said solution.

7. The process of claim 6 wherein the higher molecular weight mercaptanis butyl mercaptan.

8. The process of claim 6 wherein the lower molecular weight mercaptanis ethyl mercaptan.

9. The process of claim 6 wherein the higher molecular weight mercaptanis tertiary butyl mercaptan.

10. The process of claim 6 wherein the higher molecular weight mercaptanis isobutyl mercaptan.

HOWARD R. BATCHELDER. BERNARD H. SHOEMAKER.

CERTIFICATE OF CORRECTION.

Patent No. 2,190,007. February '15,.l9h0- HOWARD R. BATCHELDER, ET AL.

It is hereby certified that error appears inthe printed specification ofthe above numbered patent requiring correction as follows: Page 2.,second column, line 1, claim 2, for the word "presence" read process;and that the said Letters. Patent should be read with this correctiontherein that the same may conform to the record of the case in thePatent Office.

Signed and sealed this 19th day of March, A. D. l9LLO.

Henry Van Arsdale, (Seal) 2 Acting Commissioner of Patents.

